In recent years there has been great effort extended by researchers in the medical field for developing an intravenous feeding pump adapted to accurately measure and positively pump parenteral solution from a supply container into the veins of a patient without having to rely upon the force of gravity alone. Such pumps have many advantages in administering the parenteral fluid and many designs have been suggested, including two covered by patent applications of this applicant, namely, Ser. No. 431,753, filed Jan. 8, 1974 now U.S. Pat. No. 3,874,826 and Ser. No. 488,580, filed July 15, l974.
Doctors often desire to introduce drugs into the blood stream of a patient, and whenever the patient is being fed intravenously, it is usually desirable to introduce the drug through the intravenous feeding system, as by injecting into the delivery tube to the patient. Quite often the drug is of such a character that it is advisable to dilute the drug in some predetermined ratio with the volume of solution being fed to the patient. The present device is directed to that end and provides a means whereby a desired volume of drug can first be diluted in a variable volume of the parenteral solution and then fed to the patient. Then, as soon as the drug has been administered, it is usually desirable to return to the feeding of the parenteral solution. The necessary changes, of course, must be done with a minimum chance of contamination of the drug or the solution from contact with the air during the various steps of the process, and great care must be taken to prevent the feeding of air into the blood stream of the patient. The device of the present invention provides a "closed system", i.e., one in which there is no possibility of contact of outside air with the fluid. The device is one that gives an accurate reading of volume at all times.
The device of the present invention is adapted to mix a drug injection with a predetermined amount of parenteral solution, in a variable ratio, to feed the same into the blood stream of the patient and then to return to the feed of the parenteral solution without breaking the connection between the supply container of parenteral fluid and the needle which is inserted into the blood vessel of the patient. It is particularly adapted to be used in cooperation with an intravenous feeding pump, such as the ones suggested by the applicant's aforementioned patent applications, or any of the other intravenous feeding pumps which have been designed for this purpose. It is also particularly adapted to be used in such a pump utilizing the alarm system described in the applicant's pending application, Ser. No. 488,581, filed July 15, 1974, which automatically sets off an alarm signal when the supply of parenteral fluid from the pump is either closed for any reason, or the volume pumped falls below the preset quantity to be delivered.